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1. A method for performing a hybrid multiuser diversity-frequency diversity mode, the method comprising: obtaining an estimate of channel state information for a propagation channel used to transmit data to a wireless terminal; determining a confidence level that represents a potential for error between the estimate of the channel state information and true channel state information for the propagation channel; determining a preferred coherence bandwidth in a system bandwidth based on the estimate of the channel state information; mapping the confidence level to a fraction, α; allocating a first number of subcarriers in the preferred coherence bandwidth to the wireless terminal, wherein the first number is based on the fraction; and pseudorandomly allocating a second number of subcarriers outside the preferred coherence bandwidth to the wireless terminal, wherein the second number is based on a fraction, (1−α).
A method for optimizing data transmission in a wireless network by dynamically switching between two techniques: multiuser diversity and frequency diversity. First, estimate the quality of the wireless channel between the transmitter and receiver. Then, determine a confidence level representing the reliability of this estimate. Based on the channel quality estimate, identify a preferred frequency range (coherence bandwidth). A fraction, α, derived from the confidence level, determines the proportion of subcarriers within this preferred range allocated to the receiver. The remaining subcarriers, a proportion of (1-α), are allocated to the receiver using a pseudorandom method, promoting frequency diversity.
2. The method of claim 1 , wherein the confidence level is determined from the variance of the estimated channel state information.
Building on the method for optimizing data transmission by switching between multiuser diversity and frequency diversity, the confidence level (which represents the reliability of the channel quality estimate) is specifically calculated from the variance (or statistical spread) of the estimated channel state information. A higher variance indicates a less reliable channel estimate, and vice versa. This variance directly influences the fraction α, which determines the balance between allocating subcarriers based on channel quality (multiuser diversity) and random distribution (frequency diversity).
3. The method of claim 2 , wherein the variance of the estimated channel state information is determined from the mean square error of an estimate of the instantaneous propagation channel.
Further elaborating on how to determine the confidence level in the data transmission optimization method, the variance of the estimated channel state information (which is used to represent channel estimate reliability) is calculated from the mean square error (MSE) of the estimated instantaneous propagation channel. The MSE provides a measure of the average squared difference between the estimated channel and the actual channel, giving a quantitative basis for judging estimate accuracy.
4. The method of claim 2 , wherein the variance of the estimated channel state information is determined from decorrelation of a channel state in time.
Expanding on the method to find confidence level, the variance of the channel state information is determined by how much the channel changes over time (decorrelation in time). Rapid channel variations lead to greater uncertainty and a larger variance, reflecting the decreased reliability of channel state estimates. The larger the time between channel estimates, the lower the confidence level.
5. The method of claim 2 , wherein the variance of the estimated channel state information is determined from the variance of quantization noise in a limited bandwidth feedback channel.
In the data transmission optimization method, the variance of the estimated channel state information is determined from the variance of quantization noise. This noise arises from the limited bandwidth feedback channel used to communicate channel state information from the receiver back to the transmitter. The more coarse the quantization, the larger the noise variance, directly impacting the reliability of the channel estimate used for allocating subcarriers.
6. The method of claim 2 , wherein the variance of the estimated channel state information is determined from the variance of a propagation channel.
In the data transmission optimization method, the variance of the channel state information is calculated directly from the variance of the propagation channel itself. This intrinsic channel variance reflects the inherent unpredictability of the wireless environment, influencing the confidence in channel state estimates and affecting the balance between multiuser and frequency diversity allocation schemes. The greater the variance, the lower the confidence.
7. A system for performing a hybrid multiuser diversity-frequency diversity mode, the system comprising: a channel state information block configured to determine a confidence level that represents a potential for error between an estimate of channel state information for a propagation channel and true channel state information for the propagation channel, and to map the confidence level to a fraction, α, wherein the propagation channel is used to transmit data to a wireless terminal; and a multi-user time-frequency allocation block configured to allocate a first number of subcarriers in a preferred coherence bandwidth to the wireless terminal, and to pseudorandomly allocate a second number of subcarriers outside the preferred coherence bandwidth to the wireless terminal, wherein the first number is based on the fraction, α, and the second number is based on a fraction, (1−α).
A system for improving wireless data transmission by dynamically switching between two modes: multiuser diversity and frequency diversity. A "channel state information block" estimates channel quality and determines a confidence level reflecting the potential error in the estimation. This confidence level is mapped to a fraction, α. A "multi-user time-frequency allocation block" allocates a first number of subcarriers in a preferred coherence bandwidth to the receiving wireless terminal. This allocation is weighted by the factor α. The remaining subcarriers (weighted by 1-α) are pseudorandomly allocated outside this preferred frequency range.
8. The system of claim 7 , wherein the channel state information block is configured to determine the confidence level from the variance of the estimated channel state information.
Within the wireless data transmission system which balances multiuser diversity and frequency diversity, the "channel state information block" calculates the confidence level (representing the reliability of channel quality estimates) specifically from the variance (or statistical spread) of the estimated channel state information. A higher variance means a less reliable channel estimate, influencing the fraction α used to determine allocation of subcarriers based on channel quality versus random distribution.
9. The system of claim 8 , wherein the channel state information block is configured to determine the variance of the estimated channel state information from the mean square error of an estimate of the instantaneous propagation channel.
Expanding on the wireless system that switches between multiuser diversity and frequency diversity, the "channel state information block" calculates the variance of the estimated channel state information from the mean square error (MSE) of an estimate of the instantaneous propagation channel. The MSE provides a quantifiable measure of the difference between the estimated and actual channel, enabling a judgment on the estimate's accuracy.
10. The system of claim 8 , wherein the channel state information block is configured to determine the variance of the estimated channel state information from decorrelation of a channel state in time.
In the wireless system that balances multiuser diversity and frequency diversity, the "channel state information block" determines the variance of the estimated channel state information based on how much the channel changes over time (decorrelation in time). Rapid channel changes imply greater uncertainty and a larger variance, reducing the confidence in the channel estimate.
11. The system of claim 8 , wherein the channel state information block is configured to determine the variance of the estimated channel state information from the variance of quantization noise in a limited bandwidth feedback channel.
In the wireless system that balances multiuser diversity and frequency diversity, the "channel state information block" determines the variance of the estimated channel state information from the variance of quantization noise present in the limited bandwidth feedback channel used to transmit channel state information. Higher quantization noise means less accurate channel estimates.
12. The system of claim 8 , wherein the channel state information block is configured to determine the variance of the estimated channel state information from the variance of a propagation channel.
In the wireless system that balances multiuser diversity and frequency diversity, the "channel state information block" calculates the variance of the estimated channel state information directly from the variance of the propagation channel itself. This intrinsic channel variance contributes to uncertainty and affects subcarrier allocation strategy.
13. The system of claim 7 , wherein the preferred coherence bandwidth is determined based on the estimated channel state information.
Within the wireless system which balances multiuser diversity and frequency diversity, the "preferred coherence bandwidth" (the frequency range where channel conditions are relatively consistent) is determined based on the estimated channel state information. This bandwidth defines the area where frequency diversity is most important to consider.
14. A method for performing a hybrid multiuser diversity-frequency diversity mode, the method comprising: determining a confidence level that represents a potential for error between an estimate of channel state information for a propagation channel used to transmit data to a wireless terminal and true channel state information for the propagation channel; mapping the confidence level to a fraction, α; allocating to the wireless terminal a first number of subcarriers in a preferred coherence bandwidth determined based on the estimate of the channel state information, wherein the first number is based on the fraction, α; and pseudorandomly allocating a second number of subcarriers outside the preferred coherence bandwidth to the wireless terminal, wherein the second number is based on a fraction, (1−α).
A method for dynamically allocating resources in a wireless system combining multiuser diversity and frequency diversity. First, determine a confidence level that represents the reliability of the channel quality estimate. This level is mapped to a fraction, α. Then, allocate a first number of subcarriers, based on α, within a "preferred coherence bandwidth" (determined from the channel estimate) to the wireless terminal. Finally, allocate a second number of subcarriers (based on 1-α) randomly outside the preferred coherence bandwidth.
15. The method of claim 14 , wherein the confidence level is determined from the variance of the estimated channel state information.
Building upon the method for dynamically allocating resources in a wireless system, the confidence level is determined from the variance of the estimated channel state information. This variance indicates the potential error in the channel estimation process, thereby influencing the allocation of subcarriers. The confidence is inversely proportional to variance.
16. The method of claim 15 , wherein the variance of the estimated channel state information is determined from the mean square error of an estimate of the instantaneous propagation channel.
The method for dynamically allocating resources in a wireless system determines the variance of the channel estimation based on the mean square error (MSE) of an estimate of the instantaneous propagation channel. MSE is the average squared difference between estimated and true channel states.
17. The method of claim 15 , wherein the variance of the estimated channel state information is determined from decorrelation of a channel state in time.
The method for dynamically allocating resources in a wireless system determines the variance based on decorrelation of the channel state over time. If the channel changes rapidly, the variance increases, signifying less reliable channel information.
18. The method of claim 15 , wherein the variance of the estimated channel state information is determined from the variance of quantization noise in a limited bandwidth feedback channel.
The method for dynamically allocating resources in a wireless system determines the variance based on the variance of quantization noise in a limited bandwidth feedback channel. The less precise the feedback, the higher the variance, indicating lower confidence in the estimated channel state.
19. The method of claim 15 , wherein the variance of the estimated channel state information is determined from the variance of a propagation channel.
The method for dynamically allocating resources in a wireless system determines the variance directly from the variance of a propagation channel itself, which is an inherent property of the channel. The more variable the channel itself, the less reliable any estimate of it will be.
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December 2, 2014
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